Using rats in CER paradigm and working within the theoretical structure of the Rescorla-Wagner model of Pavlovian conditioning, current research deals with the associative fate of elements of simultaneous compounds composed of stimuli with a conditioning history. These experiments ask (1) what are the sufficient conditions for alteration in level of response suppression and (2) what are the precise mechanisms involved in CR change. Specific experiments involve determination of properties of stimulus events which degrade the blocking effect. What are the quantitative and qualitative aspects of these stimuli? These experiments are designed also to determine the nature of these new associations when they are formed. Experiments regarding mechanisms examine the nature of response change; are such changes associative or non-associative. Currently, the role of inhibition of delay in producing losses in conditioned suppression is being examined. These studies entail questions regarding the role of stimulus salience and generalization of inhibition of delay from compound to components.